Fan module components are protected from ice accretion using hot air bled from the high compressor. Hot air is supplied via a manifold into hollow cavities in the fan inlet case struts, thereby heating the struts and nose cone. Ultimately, this air is channeled through a series of ultrasonically drilled holes (approximately 200 per strut) to produce a hot air film on the pressure side of an inlet guide vane. This system not only taps into engine performance, but also has severely limited capability in organic matrix composite applications.
Current organic matrix composite materials capable of producing fan inlet cases are limited to maximum use temperatures of 350° F. Compressor discharge air can be significantly hotter than this limit, depending on engine speed. At ground idle, where the compressor discharge air temperature is relatively low (in icing conditions), flowing the required volume of air to anti-ice an inlet guide vane is not possible because of the limitations of the tortuous path within the inlet case manifold, struts, plumbing and valves. At maximum power, the air temperature is significantly higher, and therefore necessitates a reduction in flow so as to avoid overheating the inlet case. This reduction in flow is substantial enough to cool the hot air to a temperature too low to effectively anti-ice an inlet guide vane. Modulation has been considered and analyzed where fan discharge air would be mixed with the hotter air. This, however, has not produced satisfactory results in all cases.
Metallic inlet cases also have limitations. Erosion coatings, necessary in certain applications, have maximum use temperature limits of 450° F. Deicing can occur for more of the specified range, but the cost in performance and weight is still prohibitive.
Accordingly, it is an object of the present invention to provide an ice protection system that overcomes the above-mentioned drawbacks and disadvantages.